I really hope they didn’t finish the arc with Sam’s abilities (so far, he’s the only one of his kind who has exhibited multiple psychic abilities) with the demon possession from last week. Other than that, there aren’t too many unresolved plot points in the series.
Monster tiers (updated 05/18/2007)
Yellow Eyes (Dead)
Blonde Girl with the super, demon-killing knife
Psychics, limiter off (All dead)
Black Eyes (who had a cameo on Smallville)
Seven Deadly Sins
Shapeshifter (why always mimic Dean?)
Crazy Rogue Hunter Black Guy
Updated. Yellow Eyes drops a tier for not keeping the reaper body and what happens in the season 2 finale, and Red Eyes goes up a tier for what it acquires (or will soon). John’s Ghost added to top tier for what he does in the season 2 finale, though he technically isn’t a monster, per se. Djinn and Psychic, limiter off added to Mid Tier because they have crazy abilities. Rogue Hunter drops a tier because he got owned by cops and never came back. Black Eyes had a cameo on Smallville.
Update: Blonde girl added to mid tier for having the super knife. Seven Deadly Sins added to low tier for sucking. Red Eyes moves to the top of top tier because she has owned Dean (and, by proxy, Sam).